FIG. 1 shows the structure of a typical hybrid power output device. As shown in FIG. 1, the device comprises an engine 1, a first motor (MG1) 2, a clutch 4 and a second motor (MG2) 3 that are connected in sequence, a battery 5 electrically connected to the first motor 2 and the second motor 3, and a speed reducing mechanism (e.g., a fixed-ratio speed reducing mechanism or a variable-ratio speed reducing mechanism) 8 and a drive shaft 9 that are connected to the output end of the second motor 3. When the vehicle is driven or propelled only by the second motor 3, if the power requirement of the vehicle still can't be met, the clutch 4 must be engaged to output the power of the engine 1 so as to provide assistance.
In a conventional control method, in order to attain the condition for clutch engaging, in the process that the rotation speed of the engine is regulated solely by the engine itself, it will take a long time to attain the target rotation speed because the rotation speed control by the engine itself is lagged; in addition, severe over-control may occur in the process, i.e., oscillation of rotation speed near the ideal rotation speed for clutch engaging will occur, which will have some adverse effect to the driving comfort. During the process the engine speed increases, if the clutch is engaged when the target rotation speed is just attained but the rotation speed is still in the oscillation period, the huge impact may cause damage to the clutch even though the system response time can be shortened to a certain degree; however, if the clutch is engaged after the rotation speed of the engine is self-regulated, the dynamic system response time will be increased, i.e., a long time is required.